Ugh. As funny as Mike was (And IMHO, this RiffTrax is pretty middle-of-the-road compared to the offerings so far - good, but not great like Road House), I had a hell of a time making it through the whole thing. As it was, I had to take four breaks from the movie/RT to do something in between, and shake off the stupid I felt creeping over me from even being in the same room as this movie in any capacity. If I hadn't taken those breaks, I would have shut it off before he even reached Prague.
Oddly enough though, as much as I cringed at the choice of movie to Riff, Disembaudio was awesome. Well placed injections, didn't overpower any scenes, and had some interesting/funny commentary of his own. I think he's starting to hit his groove, and I almost feel bad for finding him so 'over the top' in T5E (though I still think he was in that case, don't get me wrong).
This is the only RiffTrax I regret buying so far, and only because the movie Riffed was such a ridiculous piece of trash that couldn't be saved, by Mike, by Joel, even by Sam Kinison if he were still alive. I'm glad I didn't buy the DVD this time around (Oddly enough, the in-laws had a copy - wonder what that says about them?). Please, Mike, Riff on more badfunny movies in the future, and fewer badstupid ones! 
Disclaimer: Opinion only; your mileage may vary.
How could you call xXx a bad movie!?!

it's obvious that you didn't watch it.

It's a ground breaking movie!
Chicago Sun-Times, Jim Emerson
"You just won't see a better acted, and better cast, movie..."
E! Online,
"...consistently fresh and gut-bustingly funny..."
Critics Reviews Average Grade: B+
Source Brief Review Grade*
Boston Globe
Ty Burr "...warms with dark laughs." more... A-
Chicago Sun-Times
Jim Emerson "You just won't see a better acted, and better cast, movie..." more... A-
Chicago Tribune
Jessica Reaves "...stellar..." more... A-
E! Online "...consistently fresh and gut-bustingly funny..." more... A-
Entertainment Weekly
Owen Gleiberman "...these are not organic characters..." more... C
filmcritic.com
Rachel Gordon "...an engaging experience." more... B+
Hollywood Reporter
Duane Byrge "...this is one of those movies that veteran moviegoers complain they don't make anymore." more... A
New York Post
Lou Lumenick "...a smart, dark road comedy..." more... B
New York Times
Manohla Dargis "...across-the-board terrific performances..." more... B
ReelViews
James Berardinelli "...movie-goers will leave the theater feeling uplifted." more... B
Rolling Stone
Peter Travers "...a scrappy human comedy that takes an honest path to laughs and is twice as funny and touching for it." more... B
Seattle Post-Intelligencer
Paula Nechak "...hilarious and astute satire..." more... B+
USA Today
Claudia Puig "It has been a while since we've seen such a consistently funny and entertaining road movie." more...